The present invention relates to a signal receiving arrangement having particular, but not exclusive use, in wideband radio signaling reception.
A well known apparatus for receiving radio signals is the traditional superhet receiver which is manually tunable over a frequency band which may be divided into sub-bands, each sub-band being selectably manually. A drawback to such a receiver is that unless one is fortuitously tuned into a frequency at which a transitory event occurs it will be missed. Also, searching over the frequency band takes a relatively long time so that the chances of detecting a transitory event having a short duration are low.
These disadvantages are overcome by a receiving arrangement in which the observable frequency band is divided into a plurality of substantially contiguous sub-bands and a narrowband receiver is allocated to each sub-band. However such an arrangement is relatively expensive in hardware and requires monitoring of the output of each receiver.
This problem can be mitigated by an arrangement in which signals in each sub-band are frequency down converted to one and the same sub-band which can be monitored by one person. However although an incoming signal of interest will be recorded/heard a difficulty arises in determining the actual frequency of the incoming signal because it is not known in which of the sub-bands the signal has occurred.